Kites

ABSTRACT

A kite uses wooden sticks having a figure-8 cross section made of two round sectioned sticks glued together side by side, producing freedom from stick breakage and uniformity of stick bending deflection, using materials available commercially in large quantities. The construction applies most advantageously to kites having strongly bent sticks and to kites of high aspect ratio and especially to kites as taught in U.S. Pat. No. 3,335,984.

United States Paten Holland, Jr.

[ KITES [76] Inventor: Raymond Prunty Holland, .lr., 1702 W.'Third St.,Roswell, N. Mex., 88201 [22] Filed: Nov. 11, 1971 21 Appl. No.: 197,838

[52] U.S. C1 244/153 R [51] Int. Cl. B64c 31/06 [58] Field of Search244/153 R, 154; 161/172; 156/166, 180; 52/730 [56] References CitedUNITED STATES PATENTS 648,544 5/1900 2,238,427 4/1941 2,442,417 6/19483,335,984 8/1967 1,021,278 3/1912 1,346,956 7/1920 Hale....l 244/154Feb. 5, 1974 1,892,985 1/1933 Hughes 244/153 R 2,785,870 3/1957 Green244/153 R 3,055,622 9/1962 Harmon 244/155 R FOREIGN PATENTS 0RAPPLICATIONS 561,856 10/1923 France 244/153 R 1,408,652 7/1965 France244/155 R Primary Examiner-Duane A. Reger Assistant Examiner-Paul E.Sauberer [57] ABSTRACT A kite uses wooden sticks having a figure-8 crosssection made of two round sectioned sticks glued together side by side,producing freedom from stick breakage and uniformity of stick bendingdeflection, using materials available commercially in large quantities.The construction applies most advantageously to kites having stronglybent sticks and to kites of high aspect ratio and especially to kites astaught in U.S. Pat. No. 3,335,984.

2 Claims, 11 Drawing Figures ll KITES The present invention relates toimprovements in kites, particularly kites having strongly bent sticksand to high aspect ratio kites requiring uniformly symmetrical wingbending in order to maintain symmetrical lateral trim in flight. Theimprovements apply especially to the type of kite taught in U.,S. Pat.No. 3,335,984, which is a kite of high aspect ratio employing an exposedforward-extending nose stick, which, until the present invention, wassubject to breakage.

The problem of obtaining good kite sticks is as old as kite flying andhas become severe as kites have been produced in large quantities andhave employed lifting surfaces of increased aspect ratio and as thesupply of defect-free straight grained wood, obtainable only from largetrees, has diminished. Especially in manufacturing high quality kites inlarge quantities the problem of obtaining good sticks has becomecritical, sometimes forcing suspension of production.

The well-known problems of breakage of kite sticks due to rough handlingby children is serious in itself,

- but the stick problem faced by the kite industry goes beyond this.Wooden sticks commonly bend unevenly, warp, splinter, and split. Eventhe best grades of lumber are not of uniform quality. The stiffness ofsticks varies from board to board, and from one end of a board to theother. Where the proper form of a kite depends on the correct relativeamount of bend of two. or more bent sticks, as in the case of highperformance high aspect ratio kites, the desired results have beenobtained only by testing each completed stick for symmetry of bend,proper stiffness, and freedom from twist. In this process, manycompleted sticks are found to be unsatisfactory and must be discarded;this is an expensive and wasteful process, unsuited to mass production.

. The basic problem of the kite stick stems from the fact that the kitestick is a very slender structural member, such that any defect, such asa tiny knot in the natural wood, causes a disproportionaly large loss ofstrength at that section of the stick, so that it snaps when bent onlyslightly. Similarly, cross grain angling only slightly out of parallelfrom the line of the stick emerges from the surface of the stick in onlya short distance, so that the stick breaks along the cross grain whenbent, or the portion of the stick having such cross grain is relativelysoft in bending, producing a stick having excessive deflections anduneven bending. Similarly, slight cross grain which would not be seriousin a member having larger cross sectional dimensions, causes the kitestick to twist when bent, the twist in turn often causing uneven bendingas one end of the stick twists over relative to the other end. Unevenbending, whatever the reason, causes correspondingly irregular flightcharacteristics in the kite.

Conventional kite sticks are sawed from boards, producing sticks havingrectangular cross sections. The saw cuts are not perfectly smooth, withthe result that the corners of the sticks are slightly ragged orserrated. From such corners, almost unavoidably, the kite flier getssplinters in his hands. If the kite stick is threaded through a hole inthe kite lifting surface material in the process of assembly, finesplinters rise from the serrated corners of the stick and snag thematerial preventing further passage of the stick, sometimes splittingthe stick. When the stick is bent, the stresses in the corners,particularly on the tension side of the stick, cause minute localfailures to occur at the discontinuities caused by the rough serratededge and the stick is made susceptible to early failure.

In the past, a large number of remedies for the faults of wooden kitesticks have been tried, none of which has been completelysatisfactory.Lumber used for cutting sticks has been hand-selected, board by board,by an expert; this is a slow expensive process unsuited to massproduction. It is especially frustrating when the supply of good boardsdwindles or disappears. Kite sticks have been milled instead of beingsawed, to round the corners to reduce splintering and splitting; thisalso increases costs. Other materials have been tried. Split bamboo istoo flexible and too heavy. The same is true of the stiffest, lightestplastic materials, such as PVC (polyvinyl chloride), even when extrudedin thin-walled section having high section moments of inertia. Plasticsfilled with fibers such as glass, (or the new carbon or boron filaments)are too expensive. Metal sticks are relatively low resistance conductorsof electricity; this introduces a prohibitive risk when a kite fallsacross bare electric wires and the kite flier attempts to recover it.

Prior to this invention, the kite stick problem was unsolved. Somequantity manufacturers of kites adopted plastic sticks for their kites,despite the fact that the resulting kites were too heavy to fly in lightwinds and too rubbery to fly in strong winds. Other manufacturersdesigned kites with straight sticks that do not bend appreciably. Mostmanufacturers limited themselves to kites of low aspect ratio which areinsensitive touneven bends in the sticks and they did not useconstruction in which the sticks pass through holes in the liftingsurface material. Others avoided sticks by the use of inflatable kites;these were of inferior flight performance because of their highaerodynamic drag and poor lift. Flexible wind-formed kites appeared,like the Scott Sled, using straight sticks and the Rogallo kite (U.S.Pat. No. 2,546,078) using no sticks at all.

In attempting to solve the stick problem the Airplane Kite Companydecided that unless plastics become stiffer, lighter and cheaper, thebest material is wood, and that some type of lamination is necessary toobtain uniformity of quality for mass production. Special plywood wasconstructed having three plies all having the grain running parallel,out of which sticks were to be sawed. Uniformity and a mass source ofsupply were achieved but the problems of corner splintering were madeworse, because now each rectangular cross section, with its three plies,had a total of twelve corners instead of four, where grain separationcould start. Lamination of wood without corners was seen to benecessary; the present invention accomplishes this resuit.

The objects of the present invention include the following:

To produce kites having sticks which a. Greatly reduce or eliminateunsymmetrical stick bending and thereby greatly reduce kite dissymmetrydue to this cause, especially on kites of high aspect ratio, on whichsuch dissymmetry produces large changes of lateral trim.

b. Greatly reduce or eliminate stick breaking, in a stick which is oflight weight and which has a high degree of structural stiffness,without the known faults of plastic or metal sticks.

c. Greatly reduce or eliminate splintering and grain separation inwooden sticks.

d. Are available in large quantities for mass production.

e. Are of uniform quality, free of damaging defects.

f. Permit insertion through the lifting surface of the kite, withoutsnagging, in the process of assembly of the kite.

g. Permit the kite design to be sporty, maneuverable and spirited in itsflight, exciting to fly, and able to strike the ground at full speedwithout stick breakage.

FIGS. 1, 2, 3 and show kites embodying the present invention. The frontor leading edge of each kite is toward the top of the paper. The kitesin FIGS. 1 and 2 are seen from above. The kite in FIG. 3 is seen frombeneath. The kite in FIG. 5 is reversible, either side serving as eithertop or bottom. I FIGS. 1 and 2 show kites as taught by US. Pat. No.3,335,984. These kites have forms which are concave upwardly, thisconcavity being present both laterally (side to side on the drawing)'andlongitudinally v(bottom to top on the drawing). FIG. 3 shows a keel kitehaving a strongly bent vwing stick, with the keellaid over to one side,for purposes of illustration, flat against the kite. FIG. 4 shows thekeel for the kite of FIG. 3. FIG. 5 shows a flexible wind-formed kitewith curved sticks.

FIGS. 6 through 11 show details of the nonsplintering laminateddual-rounded kite stick of this invention. FIGS. 6 and 7 are partialviews at sections 6-6 and 7-7, respectively, of FIGS. 1, 2, 3 and 5,showing cross sections of the wing stick and the body stickrespectively. FIGS. 8 and 10 are partial views at 8--8 and 10-10,respectively, of FIGS. 1, 2, 3 and 5. FIGS. 8 and 9show the slotting ofthe tips of the wing sticks and FIGS. '10 and 1 1 show the slotting ofthe nose sticks and body sticks.

The novel kite stick in the present invention consists of two or moresmooth-surfaced round wooden members glued together side by side fulllength along the line of tangent contact, to form a unified structuralbeam. Such a stick has no ragged or serrated edges, and has no cornerswhere stress concentrations can build up, which can cause grainseparation and splinters, leading to splitting or snapping of sticks.The sticks of this invention have smooth rounded surfaces which can bepushed through openings in the lifting surface material of the kitewithout snagging. This property enables the kite innovator to offernumerous new kites, which are light, efficient and inexpensive, usingthe new high strength synthetic fabric materials, such as the DuPontproduct, TYVEK, for the lifting surface material of the kite.

The dual structural beam construction of the kite stick provides theadvantages of lamination without the disadvantage of easy separation ofthe plies, common in conventional plywood. A defect in one of the twomembers of the beam is reinforced by the other member of the beam, sothat, with the elimination of corner stresses as described above, andwith this reinforcement against local defects, remarkably large bendscan be tolerated by the sticks without failure, and the problems ofuneven bending disappear for all practical purposes.

Flight tests comparing routine production dualrounded sticks, as taughthere, against selected high quality mahogany sticks of rectangularsection showed a clear ability of the dual rounded stick of thisinvention to maintain trimmed flight to higher wind speeds, due to theimproved symmetry of wing bending. As a result, the hand selection oflumber and the testing of sticks is no longer necessary when the newdualrounded sticks are used.

Novel kites using these new sticks make use of their property of bendingeasily in one direction while remaining stiff in a directionperpendicular to the plane of the easy bend. Typically, the body stickor longitudinal stick of a bird-like kite is installed flat relative tothe lifting surface material, in position to bend easily, concave up,and the lateral stick or wing stick is installed on edge relative to thelifting surface material, in a position to resist wing bending. Intypical rough treatment of a kite causing a stick to break, it is thebody stick which is usually broken, and not the wing stick. In thisinvention, the body stick, placed flat in the position for easy bending,is rendered immune to breakage. Tests were made of kites like FIGS. 1and 2, having projecting nose sticks of the new dual-round construction.These test kites were deliberately flown straight down into the groundin high winds. The kites hit the ground and bounced. In no case wasthere a stick failure. Kites of this invention have been testedintensively over an elapsed period of six months, and no stick has yetbroken in testing.

The new dual-round kite sticks have also proven to be attractive formanufacturing. Individual members of the sticks are often crooked, yetthe unified dual stick is straight. The supply problem is solved; goodquality birch dowels for use in making these sticks can be obtainedwithout delay in quantities up to car loads. Unlike plastics, the sticksare stiff and light. Unlike metals, they are not good conductors ofelectricity. They permit the kite innovator to use strongly bent sticks,and to use long slender wings, making the best aerodynamic formsavailable for kites.

Now referring specifically to the drawing:

In FIG. 1 a bird kite of this invention is shown, consisting of liftingsurface 1 of a bird-like silhouette, supported by dual-rounded lateralbeam 2, serving as the wing stick, and dual-rounded longitudinal beam 3,serving as the body stick. Wing stick 2 is placed on edge and body stick3 is placed flat relative to lifting surface 1. Border string 4 forms aclosed loop engaging slots in the ends of sticks 2 and 3, and is securedto lifting surface 1 by means of several lengths of adhesive tape 5. Thekite is seen from above; the ends of sticks 2 and 3 are higher thantheir midsections, producing a general upward-facing concavity in thekite surface both laterally and longitudinally. Wing stick 1 is alsobent rearward at the tips, producing rearward-facing concavity in thisstick. Sticks 2 and 3 are bound together where they cross. An opening isprovided in surface 1 just rearward of the point where the sticks cross,to permit the flying string beneath the kite to be tied up around stick3 at that point. The construction shown in FIG. 1 is suitable for kitesusing a soft plastic film material for lifting surface 1.

FIG. 2 shows another bird kite of somewhat different construction,suitable for use with a strong tearresistant material for liftingsurface 1, with features suitable for large kites. Wing sticks 7, nosestick 8, and body stick 9 engage in central four-way socket fitting 6which is attached adhesively to lifting surface 1. The

use of the central fitting 6 reduces the maximum stick length andresulting package length to about half of that otherwise required. Wingsticks 7 and body stick 9 are each threaded through two holes 10 inlifting surface 1, to position them accurately and to stabilize themagainst sideward buckling. Each of wing sticks 7 engages lifting surface1 by means of a slot at its outer end, entering a hole in the wing tipregion of lifting surface I. The rearmost portion of body stick 9 fitsin a socket formed of adhesive tape attached by such tape at the tail oflifting surface 1. In FIG. 2 nose string 11 is taped to lifting surface1 at the shoulders of the bird-like silhouette. The functions performedby border string 4 in FIG. 1 are performed by nose string 11 and thetough material of lifting surface 1 in FIG. 2.

FIG. 3 shows a keel kite making use of multiple holes in tough tearresistant lifting surface 1 through which wing stick 2 is threaded,giving stick 2 a pronounced curvature. Stick 12, which may be a simpleround sectioned dowel of small size, is threaded through matching holesin lifting surface 1 and in keel 13, which is also made of tearresistant material, lacing these parts together securely. The ends ofstick 12 are slotted; each slot engages two thicknesses of tearresistant material, one thickness of the lifting surface 1 and onethickness of the keel 13.

FIG. 4 shows keel 13 from FIG. 3 laid out fiat. Holes 14 through whichstick 12 is threaded (FIG. 3) may be seen to lie along a curved line.The function of the curve is to place more tension in some portions ofthe keel than in other portions, and to use this distribution of tensionto bend stick 12 to the cambered line required by the kite design. Whenthe kite is flying and the wind is light stick 12 tends to straighten,causing portions of keel 13 to go slack. When the wind is stronger, andstring tension is greater, slackness disappears from the keel and thedesired camber is produced in stick 12 and in lifting surface LBy meansof the cambered keel, as described above a response to wind speed isachieved which the kite designer may use advantageously both in lightwinds and strong winds, applying well known aerodynamic principles. Itmay be seen that the kite of FIG. 3 consists entirely of surface partswhich may be stamped out, and round sectioned sticks, and requires nofactory assembly labor, this invention thereby permitting the kite to beproduced at low cost.

In FIG. 5, a wind formed kite is shown, also of low cost construction.Tear resistant lifting surface material is used, through whichdual-rounded sticks 15 are threaded, and engaged to the surface materialby means of slots at their ends. The surface material is stretched outflat, laterally, bending sticks 15 as shown.

Sticks 2, 3, 7, 8, 9, and 15 as shown in FIGS. 1, 2, 3, and 5 are all ofthe dual-rounded construction, and stick 12 in FIG. 3 would also be ofthis construction if the bend imposed on it by keel 13 were very large.

FIG. 6 is a partial sectional view showing the cross section of the dualrounded stick, taken at sections 6-6 of FIGS. 1, 2, 3, and 5. At theselocations, the dual-rounded stick is in its stiff position, on edgerelative to the lifting surface, supporting the wing in FIGS. 1, 2, and3.

FIG. 7 is a partial sectional view, taken at sections 7-7 of FIGS. 1 and2. In these locations the dualrounded stick is in a position for easybending, lying flat relative to the lifting surface.

As described previously, the dual rounded stick is a unified structuralmember consisting of long roundsectioned sticks in tangent contactside-by-side, forming a figure-8 structural cross section, rigidly gluedtogether along substantially the entire lengths of the two roundmembers, along the line of tangent contact. As compared to conventionalplywood the glue area between the glued parts is much reduced while theresults are improved. No evidence of glue is apparent on the completeddual-round stick.

The individual members which make up the dual stick are smooth, and freefrom all corners edges, splinters, and splits. The assembled dual stickis similarly free of these defects so that the dual stick may bethreaded through holes in the lifting surface material without snaggingand without cutting or sawing the material. As structural beams theproperties of the dualrounded sticks of FIGS. 6 and 7 are superb, due tothe elimination of corner stresses, splintering, and splitting, and alsodue to the FIG. 8 cross section, producing a stiff direction ofinstallation (FIG. 6) and a flexible direction of installation (FIG. 7).Uniform bending and freedom from stick breakage are achieved by thisconstruction, as described earlier.

FIG. 8 is partial view taken at 8-8 of FIGS. 1, 2, 3 and 5, showing tipslots 6 at the ends of the dual-round stick when it is installed in itsstiff position, edgewise to the general plane of the lifting surfacematerial.

FIG. 9 is a side view of the dual-round stick showing the same slottingas in FIG. 8. Either one of these two slots is used, avoiding a slotwhich would place a load on the glued joint between the tworound-sectioned members.

FIG. 10 is a partial view taken at 10-10 of FIGS. 1 and 2, showing tipslot 17, at the end of the dual round stick when it is installed flatrelative to the lifting surface material, in its easily bent position.

FIG. 11 is a side view of the dual-round stick showing the same slot asin FIG. 10.

I claim:

1. A kite comprising a lifting surface, a longitudinally positionedstick supporting said lifting surface, and a generally triangular keelbeneath said kite, said keel being attached to said kite by said stickthreaded through holes along the upper edge of said keel and throughmatching holes in said lifting surface.

2. In the kite of claim 1, said holes along the upper edge of said keelbeing arranged along a curved line, to distribute tension in said keelmember and to distribute bending in said longitudinally positioned stickmember,

as described.

1. A kite comprising a lifting surface, a longitudinally positionedstick supporting said lifting surface, and a generally triangular keelbeneath said kite, said keel being attached to said kite by said stickthreaded through holes along the upper edge of said keel and throughmatching holes in said lifting surface.
 2. In the kite of claim 1, saidholes along the upper edge of said keel being arranged along a curvedline, to distribute tension in said keel member and to distributebending in said longitudinally positioned stick member, as described.